org.apache.nifi.util.text.DateTimeMatcher Maven / Gradle / Ivy
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.nifi.util.text;
/**
*
* A utility class that can be used to determine whether or not a String matches a given date/time format, as specified
* by the Time Format used in {@link java.text.SimpleDateFormat}. It is not uncommon to see code written along the lines of:
*
*
*
* final String format = "yyyy/MM/dd HH:mm:ss.SSS";
* try {
* new SimpleDateFormat(format).parse(text);
* return true;
* } catch (Exception e) {
* return false;
* }
*
* This approach, however, is frowned upon for two important reasons. Firstly, the performance is poor. A micro-benchmark that involves executing
* the above code (even reusing the SimpleDateFormat object) to evaluate whether or not text is a timestamp took approximately 125-130 seconds
* to iterate 1,000,000 times (after discarding the first 1,000,000 iterations as a 'warmup'). As a comparison, this utility takes about 8-11 seconds against
* the same data and on the same machine.
*
*
*
* Secondly, the above snippet has a very expensive side effect of throwing an Exception if the text does not match the format. This Exception is silently ignored,
* but can have devastating effects on the JVM as a whole, as creating the Exception object can result in requiring a Safepoint, which means that all threads in the JVM
* may be forced to pause.
*
*
*
* Note, however, that this class is not intended to replace SimpleDateFormat, as it does not perform the actual parsing but instead only determines whether or not
* a given input text matches the pattern, so that if it does, a SimpleDateFormat can be used parse the input.
*
*/
public interface DateTimeMatcher {
/**
* Determines whether or not the text matches the pattern
* @param text the text to evaluate
* @return true if the text matches the pattern, false otherwise
*/
boolean matches(String text);
static DateTimeMatcher compile(String format) {
if (format == null) {
return t -> false;
}
return new DateTimeMatcherCompiler().compile(format);
}
}